This invention relates to implantable tissue expanders and prostheses, and more particularly to implantable mammary soft tissue expanders and prostheses.
Tissue expanders are devices that are implanted beneath the skin and then gradually inflated to stretch the overlying tissue. Such expanders are used to create a pocket for receiving a permanent prosthesis and to generate an increased skin surface area so that skin can be utilized for grafting or reconstruction.
Implantable tissue expanders are commonly formed of a silicone polymer shell. After implantation, saline or some other fluid is periodically injected into the expander, for example, through an injection port, by a needle that pierces the overlying skin. In addition, the shell can be partially filled with fluid or gel prior to implantation.
A tissue expander can be provided with an injection port, for example, a port comprising a septum, that can be pierced with a hypodermic needle for the introduction of fluid into the expander. However, it can be difficult to accurately locate the injection port through the overlying tissue. If the injection port is missed and the needle punctures the shell of the tissue expander, the expander can leak. Most often, this requires that the expander be removed and replaced. This problem can be addressed by providing an injection port that is remote from the tissue expander, but is in fluid communication with the expander. Such systems are described in U.S. Pat. No. 4,190,040. Other solutions include eliminating the need for an injection site altogether by forming the expander with a self-sealing shell that can be pierced with a hypodermic needle at any point for the purpose of adding fluid to the shell. For example, U.S. Pat. No. 5,066,303 describes an expander formed using a self-sealing shell material that reportedly can be safely pierced in any location.
The tissue expander of the present invention contains a self-sealing area surrounding an injection port. This self-sealing area reduces the risk of causing a leak in the expander when the hypodermic needle used to fill the expander misses the injection port. This feature reduces the frequency with which expanders require removal due to leakage caused by inadvertent punctures.
The invention features a mammary tissue expander comprising a shell having an anterior face and a posterior face, the anterior face having an upper pole portion and lower pole portion meeting at an apex, the prosthesis comprising a self-sealing material bonded to the shell within the upper pole of the anterior face of the shell to create a self-sealing region of the expander that is self-sealing after needle puncture. The expander can further comprise a injection port located within the self-sealing region of the expander.
In certain embodiments, the self-sealing material bonded to the shell acts to permit controlled directional expansion of the expander, self-sealing material is a unitary body comprising at least one layer of fabric and at least one layer of elastomeric material impregnated with a swelling agent, the fabric restraining expansion of the elastomeric material, at least a portion of the outer surface of the shell is textured, shell comprises silicone, the fabric is a knitted fabric, the fabric is a woven fabric, the fabric is a non-woven or spun-bonded fabric, the fabric is a crocheted fabric, the fabric is a polyester fabric, the swelling agent is dimethylpolysiloxane, the self-sealing material comprises at least two layers of fabric and at least two layers of elastomeric material, and the self-sealing material comprises at least two layers of fabric and at least three layers of elastomeric material.
The invention also features an improved method for introducing a swelling agent into an assembly comprising at least one layer of fabric and at least one layer of elastomeric material, the method comprising: a) providing an assembly comprising at least one layer of fabric bonded to at least one layer of elastomeric material; and b) immersing the assembly in a swelling agent under conditions of reduced atmospheric pressure for a time sufficient to allow the swelling agent to enter the at least a portion of the elastomeric material. In certain embodiments, the elastomeric material is silicone and the swelling agent is dimethylpolysiloxane.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. All of the patents and references cited herein are hereby incorporated by reference in their entirety.